What you should know about SP flash tool is that you shouldn’t interrupt
a flash or read back process. If you do, the phone will go off and not
come on at all. You might get the “USB device not recognized” error
on further flashing attempts. If somehow, the process got interrupted
and you now have a totally dead phone on your hands, don’t panic. All
you need to do is connect the phone to a computer (via a USB cord) or

power source and leave it to charge for some time. It could take up to
two hours but once the phone is revived, your battery could read as low
as 1% . just leave it to keep charging before powering it up.

Tips to speed things up

* Remove the battery > Connect the phone to a charger without battery
inside > Slot in the battery while the phone is still connected to
the charger
* You could keep pressing the Volume up + Power button while charging
* You could remove and boost the battery using a desktop / external charger then resume internal charging.
* Uninstall then re-install MTK preloader vcom drivers using this guide @ how-to-manually-install-Mediatek & spreadtrum.html